1. Field of the Disclosure
Embodiments of the present disclosure relate to Fe-based amorphous magnetic alloys and magnetic sheets. In particular, embodiments of the present disclosure relate to an Fe-based amorphous magnetic alloy having a large imaginary part μ″ of complex permeability for use in a highly flexible magnetic sheet and a magnetic sheet incorporating the Fe-based amorphous magnetic alloy.
2. Description of the Related Art
Generally, alloys based on TM-Al—Ga—P—C—B—Si (TM represents a transition metal element such as Fe, Co, or Ni) and/or other similar element form amorphous phases and become amorphous soft magnetic alloys by being quenched in a molten state. Techniques for fabricating magnetic materials with excellent magnetic properties may be developed by optimizing the composition of the amorphous soft magnetic alloys. An Fe-based amorphous magnetic alloy has been developed where the alloy may be used as a magnetic material with excellent magnetic properties, in particular, a magnetic material having a large imaginary part μ″ of complex permeability (refer to Japanese Unexamined Patent Application Publication No. 2002-226956).
Portable electronic devices such as cellular phones and laptop computers are increasingly used. These portable electronic devices face problems of electromagnetic wave interference, and there is increasing need for measures for preventing generation of unwanted high-frequency electromagnetic waves. In order to suppress unwanted electromagnetic waves, attaching a magnetic sheet to an electronic device that generates unwanted electromagnetic waves is effective. This magnetic sheet is prepared by forming particles of several to several tens of micrometers in size from the above-described Fe-based amorphous magnetic alloy by a water atomization process or the like, flattening the particles, kneading the resulting particles with a matrix material (insulating resin) such as polyethylene chloride serving as a binder, and forming the resulting mixture into sheets of several tens to several hundred micrometers in thickness by a doctor blade technique. This magnetic sheet preferably has a complex permeability with a large imaginary part μ″ in the operation frequency band.
The imaginary part μ″ of complex permeability of the Fe-based amorphous magnetic alloy may be increased by annealing. The problem associated with this is that when the glass transition temperature (Tg), the crystallization temperature (Tx), and the melting temperature (Tm) of the Fe-based amorphous magnetic alloy are high, the annealing temperature must be also high. Accordingly, when the Fe-based amorphous magnetic alloy is used in the magnetic sheet, the matrix material may become thermally decomposed and deteriorated, resulting in embrittlement of the magnetic sheet.